Many heavy vehicles such as trucks and buses include air brake systems which utilize compressed air. Compressed air brake systems typically include a compressor that draws in atmospheric air and compresses it for use by the brake system components. Air that is drawn into the compressor usually includes water vapor and other contaminants. These contaminants should be removed from the compressed air before the compressed air enters the brake system to prevent freezing or other negative consequences. Removal of solid, liquid, and vapor air system contaminants can be accomplished by installing an air dryer system. Air dryers typically utilize a filter and a desiccant to collect and remove water and other air system contaminants before they enter the brake system, thereby providing clean, dry air to the system components that utilize compressed air.
Moisture that is removed from compressed air by an air dyer system is typically expelled from the air dryer itself by a valve referred to as a purge valve. The purge valve is usually located at the bottom of the air dryer base and remains open during compressor unload cycle. The purge valve allows collected moisture, condensation, and contamination to be expelled from the air dryer during a purge cycle. Thus, the purge valve is an important component of an air dryer system. However, due to the nature of their construction, which usually involves an expensive rubber to metal bonding step, purge valves typically represent a significant portion (e.g., 15-25%) of the total cost of the air dryers used for heavy vehicle air brake systems. Purge valves also contribute significantly to the overall size of the air dryer. Thus, while the currently used purge valves are effective for their intended purpose, a need exists for a smaller, less-expensive purge valve that is compatible with existing air dryer systems and technology.